Weed Management Plans for Horse Pastures

An effective weed management plan should consider the purpose of the pasture, weed species and abundance, which weeds should be controlled and how, and sources of information.

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The fall is a good time to evaluate your horse pasture’s quality because it’s easy to see which weeds were most prevalent and uncontrolled during the summer and are now large and seed-producing. It is also a good time to develop a weed management plan for pastures during the coming year. An effective weed management plan should consider the following items: the pasture’s purpose, weed species and abundance, which weeds should be controlled and the method of weed control, and sources of information.

Purpose of the pasture: If the pasture is a significant portion of your horses’ diet, you will want a high-quality, nearly weed-free forage. Conversely, a “pasture” maintained as a drylot for feeding horses will contain many weeds but there is little reason to control them, as there are few, if any, desirable forages in a drylot. Kentucky property owners typically maintain their horse pastures between these two extremes. The questions of “why are these weeds in my pasture?” followed by “what should I do about weeds in the pasture?” are asked frequently. Forages grown with adequate fertility that are not overgrazed will limit weed occurrence but will not prevent all weeds from growing.

Weed species, abundance, and distribution: Plants that we call weeds grow in ecological niches. This means an environment exists that allows for germination, vegetative growth, and maturation. Horse pastures provide several of these ecological niches that allow some weeds to thrive. Kentucky is located in the temperate transition zone that allows warm-season or cool-season plants to grow. Warm-season weeds germinate in spring or early summer, grow, and produce seeds before frost. Cool-season weeds germinate and produce some growth in the fall and produce seeds the following spring or summer. The many cool- and warm-season weed species provides horse pasture managers with the challenge of determining what weeds, if any, they should be controlling in a pasture. The most abundant weeds in horse pastures usually are annual species that produce thousands of seeds. Spiny pigweed, also known as spiny amaranth, produces more than 100,000 seeds per plant. This weed is widespread and grows most often in compacted areas along fences and around feeding and watering areas of pastures. Spiny pigweed also is a good example of weeds’ “patchiness,” meaning the only grow in certain portions of the pasture where their ecological niche occurs.

Which weeds to control and method and time of weed control: Generally, you should remove from pastures all poisonous weeds and weeds that inhibit grazing. Poison hemlock, for instance, grows across Kentucky and is toxic to horses and other animals. Although horses rarely eat poison hemlock, property owners should remove it. Musk thistle and bull thistle grow throughout Kentucky and inhibit grazing. Canada thistle occurs less frequently but also inhibits grazing and is more difficult to control. Large crabgrass and yellow foxtail are warm-season summer grasses. Horses graze the large crabgrass but not yellow foxtail. Buckhorn plantain is a cool-season plant that horses consume when pasture grass is limiting. Horse will readily consume any small, tender “weeds” but rarely consume them as large plants.

Methods of removing horse pasture weeds include hand removal, mowing, and herbicide application, and each has its advantages and disadvantages. Hand-weeding can be very effective and is particularly useful for removing poisonous plants, such as poison hemlock, from the pasture. Poisonous plants need to be controlled but should also be removed from the pasture to prevent animals from consuming them. The downside of hand-weeding is that the process is slow and inefficient for large areas. Mowing is rarely effective for killing weeds in pastures—mowing low enough to kill the weeds (2 inches or less) removes valuable forage. Mowing heights of about 6 inches will keep some large weeds from producing seeds but does not control smaller weeds. Herbicides are efficient and provide excellent control, but in areas of the transition zone such as Kentucky, there is not one herbicide that will control all the weeds with one treatment.

There are optimum times to control weeds with herbicides. The following months are the preferred times for herbicide treatment of several weedy species in Kentucky:

Consult your local Cooperative Extension Service agricultural agent for specific information on herbicides in your area. Remember, not all herbicides are registered for use in all states and countries so read the label carefully, and follow all directions. Many Cooperative Extension Services have publications regarding weed control in pastures. Examples of such publications are: